1. Field of the Invention
The invention relates to buckstay systems for steam generation apparatus, for example for use with large boilers that are supported by a frame.
2. Description of Related Art
Boilers are commonly constructed of tube banks forming side walls, and typically planar side walls defining a structure of polygonal and usually rectangular section. As the system reaches operating temperature, the walls expand vertically and horizontally. Additionally, furnace pressure variations, pressure differential between fireside and ambient, may produce additional flexing of the tube walls either inwardly or outwardly.
To accommodate gas pressure differential and like effects the boiler walls are typically supported on the outside by an arrangement of members that surround the boiler to provide additional support to the boiler wall and limit the deformation of the wall in a horizontal direction attributable to pressure variations. The arrangement typically uses both vertical and horizontal members that are respectively known as vertical and horizontal buckstays.
Typically, horizontal buckstays are disposed in bands around the perimeter of the boiler walls at vertically spaced intervals. Horizontal buckstays surrounding the boiler at a given level walls are mechanically tied. Thus as the boiler flexes in a horizontal direction the reaction of one buckstay is resisted by the reactions of the buckstay on the opposing wall. Vertical buckstays are provided to connect series of adjacent horizontal buckstays and complete a buckstay support structure. These may be adapted at least at some points with a connection that permits a sliding action to allow relative movement between the wall and the buckstays. As the boiler expands in a vertical direction this accommodates a variable effect on the various levels of buckstays.
The typical boiler has planar walls meeting to form corners. There is a requirement to effect a connection between horizontal buckstay members where a first wall meets a second wall at an angle to form a corner. Conventionally, horizontal buckstays are continuous elongate structural members such as I-beams spanning the length of an associated wall with buckstays associated with adjacent walls extending at the corner formed by the adjacent walls to be connected by means of corner assemblies. The corner assemblies require potentially complex arrangements of links and brackets to accommodate differential expansion between a “hot” boiler wall and “cold” buckstays. An example of such a corner assembly can be seen in FIGS. 1 and 2.